Control system for hydraulic pumps supplying hydraulic fluid to double-acting rams of hydraulic presses



May 17, 1949. H. F. M MlLLlN 7 CONTROL SYSTEMS FOR HYDRAULIC PUMPS SUPPLYING HYDRAULIC FLUID TO DOUBLE-ACTING RAMS F HYDRAULIC PRESSES Filed July 10, 1944 4 Sheets-Sheet 1 l" I E:E 5o! 63- 59 502 i4 ,g I 500225 9092 7 51 7/5 57 9) 93 60 59 90 94- 52 0'4 L 99 39 A L 96, w,

67 a2 a GI 77 68 INVENTOR Howmw FI MacMuuu ATTORNEYS May 17, 1949. H. F. M MlLLIN 2,470,357

CONTROL SYSTEMS FOR HYDRAULIC PUMPS SUPPLYING HYDRAULIC FLUID TO' DOUBLE-ACTING V RAMS OF HYDRAULIC PRESSES Filed July 10, 1944 4 Sheets-Sheet 3 453 l 4 I 4 7438 425 f/ 439 'INVENTOR HOWARD F. MncMlLLIM BY I mEQEYS Patented May 17, 1949 UNITED STATES PATENT OFFICE.

CONTROL SYSTEM FOR HYDRAULIC PUMPS SUPPLYING HYDRAULIC FLUID "IO DOUBLE-ACTING RAMS OF HY- DRAULIC PRESSES Howard F. MacMillin, Mount Gilead, Ohio, as-

signor to vH-P-M Development Corporation, Wilmington, Del., a corporation of Delaware Application July 10, 1944, Serial No. 544,221.

20 Claims. 1

This invention relates to control systems for hydraulic pumps, and more particularly relates to control systems for hydraulic pumps that supply hydraulic fluid to a double-acting ram of a hydraulic press.

An object of the invention is to provide a control system for a pump of a hydraulic system wherein trapped hydraulic fluid and release of the trapped fluid controls the flow of hydraulic fluid from the pump to a hydraulic motor.

Another object of the invention is to provide a hydraulic control system for a variable capacity pump wherein trapped hydraulic fluid and release of the trapped fluid controls the delivery of hydraulic fluid from the pump.

Another object of the invention is to provide wherein release of the trapped fluid either in response to a predetermined pressure developed by the pump, or in response to a predetermined position of an actuated element operated by the pump, will revers the delivery of the pump, and also wherein the actuated element is connected to the pump to shift the same to neutral and thereby stop delivery of fluid under pressure from the pump.

Another object of the invention is to provide a control system for a hydraulic press in accordance with the foregoing object wherein hydraulic fluid is readmitted into the fluid-trappin chamher when the ram of the press has completed a retraction stroke to thereby automatically start a hydraulic control system for a hydraulic pump to regulate the discharge of hydraulic fluid from the pump wherein trapped fluid places the pump on a delivery stroke, and pressure developed on the discharge side of the pump causes release of the trapped fluid to change the stroke of the pump.

Still another object of the invention is to provide a hydraulic control system in accordance with the foregoing object wherein the release of the trapped fluid is occasioned by pressure built up in response to operation of the ram of the press or in response to the position of the platen of the press that is operated by the ram.

Still another object of the invention is to provide a control system in accordance with the foregoing object wherein the release of the trapped fluid is brought about selectively for occasioning either position-reversal Or pressurereversal of th ram of the press. I

Still another object of the invention is to provide a hydraulic system in accordance with the foregoing object wherein the operation of the press may be either semi-automatic or fullautomatic and wherein the ram of the press can be reversed either in response to a predetermined position of the ram in its stroke of operation or in response to a predetermined pressure that is built up upon the ram during operation thereof.

Still another object of the invention is to provide a control system in accordance with the foregoing object wherein the volume of the chamber containing the trapped fluid is changed during operation of the hydraulic press to cause a slowdown movement of the ram in its stroke of operation.

Another object of the invention is to provide a control system wherein trapped hydraulic fluid places a variable delivery pump on stroke, and

the ram on a new cycle of movement as caused by a shifting of the pump when hydraulic fluid recharges the trapping-chamber.

Another object of the invention is to provide a control system in accordance with either of. the two foregoing objects wherein the volume of the trapping-chamber that confines the trapped fluid for operating the pump can be changed to produce a change in the stroke of the pump and thereby obtain a slow-down operation of the ram of the press.

Still another object of the invention is to provide a hydraulic control system for a hydraulic press substantially in accordance with the foregoing objects wherein the control system is adapted to operate a valve for shifting the direction of flow of hydraulic fluid to the ram of a hydraulic press as supplied by a uni-directional discharge pump.

In the drawings:

Figure 1 is a diagrammatic view of a hydraulic control system embodying the features of this invention showing the manner in which operation of a pump is controlled by release of trapped fluid in response to a predetermined pressure on the discharge side of the pump.

Figure 2 is a diagrammatic view of a hydraulic control system embodying the features of this invention as applied to a hydraulic motor illustrating the manner in which the hydraulic motor can be placed through a single cycle of operation.

Figure 3 is a diagrammatic view of a hydraulic control system embodying the features of this invention as applied to a self-centering variable delivery pump for controlling operation of the pump in response'to pressure developed on either side thereof upon reversal of flow through the Figure 4 is a diagrammatic view of the hydraulic control system as applied to a hydraulic press wherein shifting of the delivery of the hydraulic pump causes retraction of the ram of the press and the pump is placed on neutral at the end of the return stroke of the ram.

Figure 5 is a diagrammatic view-of the hydraulic control system similar to that disclosed in Figure 4 but which includes the additional features of position reversal of the ram, as well as pressure reversal, a high pressure release and pump by-pass at the end or the pressing-stroke of the ram.

Figure 6 is a diagrammatic view of the hydraulic control system as applied to a hydraulic press similar to Figures 4 and 5 but with the additional features of full-automatic operation of the hydraulic press together with a slow-down operation of the ram in its cycle of movement.

Figure 7 is a diagrammatic view of the hydraulic control system of this invention as applied to a. hydraulic press having a uni-directional flow fluid source and a 4-way valve for directing the flow of fluid to the press.

Figure 8 is a cross-sectional view of one the control valves of the hydraulic system.

Figure 9 is a cross-sectional view of a modified arrangement of the fluid-trapping control chamber for controlling the direction of flow of fluid to the ram 01' a hydraulic motor.

Figure 10 is an enlarged view of the camoperating devices illustrated in Figure 7 that are attached to the platen of the press.

In Figure 1 there is shown a simplified hydraulic control system for a variable delivery pump wherein fluid is trapped within a chamber for placing the pump on a discharge stroke and for retaining the pump on the discharge stroke until a predetermined pressure is built up in the discharge side of the pump that is applied to the trapped fluid to thereby cause discharge of the trapped fluid from the trapping chamber and permit the pump to move to neutral or norlischarge position.

In Figure 1 the hydraulic system consists of a pump iii that is of the uni-directional variablecapacity type wherein hydraulic fluid is drawn into the pump through the suction line I! from the tank 32 and is discharged through the discharge line H to the hydraulic motor H. The pump is termed a uni-directional pump because the discharge of the hydraulic fluid from the pump is always in the same direction through the discharge line I3. The variable-capacity feature of the pump it is a well-known feature of variable delivery pumps wherein there is provided a control ring I! for operating the mechanism within the pump to change the pumping capacity of the pump mechanism. Pumps of this type are usually provided with a plurality of radially disposed cylinders that are moved relative to the central axis of the pump to change the stroke of the pistons in the cylinders and thereby alter the discharge from the pump. The cylinders are controlled by the control or shiftring 15. Such pumps are of a well-known type and further description thereof is not deemed necessary.

The discharge line I: from the pump III is connected to a flow-reversing valve l6 that in turn is connected to the hydraulic motor ll by means of the conduits l1 and I8. The flow-reversing valve has a spool l9 therein that is arranged so that when in position as shown in Figure 1, the discharge line l3 from the pump is connected to the conduit I8, and the conduit l1 from the motor 14 is connected to the discharge line 20 that is also connected to the valve 16 by the conduits 2| and 22. When the spool I9 is in the left-hand position in the valve ii the discharge conduit I3 is connected to the conduit 11 and the conduit I! of the motor I will then be connected to the exhaust line 20 and thereby obtain a reversal of The control system for the uni-directional I variable delivery pump ill consists of a piston 28 that is reciprocable in the cylinder 28 attached to the casing 01' the pump ID. The piston 25 carries a plunger 21 that has areduced-diameter portion 2| connected to the control member or shift-ring ll of the pump 10. The shoulder 29 of the plunger 21 limits the direction of movement of the piston 25 in a rightward direction and thereby controls the maximum stroke position of the shift-ring or controlling member II. A spring 30 is located between the piston 25 and the casing of the pump Ill to urge the piston 25, and thus the plunger 21, in a leftward direction to place the shift ring in a neutral position and thereby stop delivery of fluid under pressure from the pump 10. When the pump in is in neutral position the mechanism thereof will be operating but because the pumping mechanism is coaxial with the axis of the pump at this time, there will be no fluid delivered by the pump.

The piston 25 divides the cylinder 28 into two chambers 31 and 32. The chamber 32 is connected to the discharge line l3 of the pump l0 by means of a conduit 33 whereby the chamber 32 receives fluid under pressure from the conduit i3 so that the chamber 32 is retained at the same pressure that exists in the discharge line i3.

The chamber 3| in the cylinder 26 is the fluidtrapping chamber in which fluid is placed for entrapment to place the pump on stroke, and from which release of the trapped fluid will permit the spring 30 to move the pump to or toward neutral position.

The fluid-trapping chamber ii is connected to a pilot pump 35 by means of the conduits 36, 31 and 38 whereby the pilot pump 35 may deliver fluid under pressure into the fluid-trapping chamber 3| as received from the tank 12 through the conduit 2!. A control valve 40 is placed between the conduits 38 and 31 to shut oil the supply of fluid from the pilot pump 35 to the trapping-chamber 2| when the spool ll of the valve 40 is in the position illustrated in Figure 1. At this time, the discharge from the pilot pump 35 is relieved through the conduit 42 to the tank I2 as regulated by the pressure-relief valve 43, which thereby maintains a substantially constant pressure in the conduit 38.

The fluid-trapping chamber 2| is also connected to the tank 12 through a conduit 44 in which there is placed a pressure relief valve 45 so that fluid under pressure can be discharged from the fluid-trapping chamber 3| through the conduits 36, 31 and N to the tank I2 under control of the pressure relief valve 45.

The pressure-relief valves 43 and 45 are adjustable to regulate the point at which they will open to permit flow of fluid through the same.

The fluid-trapping chamber 3| is also connected to the tank [2 through the conduit 4' under control oi the valve 41 that has a spool i 8 ll therein for closing the conduit II and prevent flow of fluid to the tank I! when the spool isinthepositionlistedinl'igure 1. v

The pilot pump 35 together with the main pump ll may be driven by any suitable power means, and the pilot pump 35 maybe of the variable delivery type having control means to move the pump mechanism toward neutral or no-,

delivery position when a predetermined pressure exists in the discharge side of the pump.

The neutral or no-discharge position of the shift ring it is with the ring It disposed on the axial center of the pump ll, thus placing the piston 25 toward the left-hand end of the cylinder 2B, the hydraulic fluid in the trappingchamber 3| having previously exhausted from this chamber due to prior operation of the hydraulic control system. Thus, when the pump II and the pump 35 are-started, the pump 35 will build up pressure in the discharge line 38 but thepuinp llwillrunidle.

The spool ll of the valve ll is then moved in a rightward direction to open the conduit 38 to the conduit 31 and thus supply fluid under pressure into the chamber 3| of the control cylinder 26. The fluid under pressure in the chamber 3| moves the piston 25 in a rightward direction to shift the shift-ring l5 and place the pump III on a discharge stroke by which fluid under pressure is delivered through the discharge line l3. The spool Ii is then released and the spring for actuating the same returns the spool to the position illustrated in Figure 1, thus cutting oil. the supply of fluid under pressure to the chamber 3| and trapping fluid therein because the relief-valve It will not at this time permit discharge of fluid from the trappingchamber 3 i With the valve IS in position as illustrated in Figure 1, fluid under pressure is delivered to the hydraulic motor ll through the discharge line it and the conduit 18, fluid from the opposite side of the motor being discharged through the conduits ii and 2B for return to the tank l2.

The fluid that is trapped in the chamber 3! will retain the pump it on discharge stroke until the fluid is released or exhausted from the chamber 3i.

There are two ways by which fluid may be discharged from the chamber 3|, one of which uses the pressure in the discharge line I3 for exhausidng the fluid from the trapping-chamber ii to change the discharge of the pump in response to a predetermined pressure in the discharge line i3 to move the same to neutral, and a second, is the valve 41 which can cause an immediate discharge of the fluid from the trapping chamber 3i and thus cause the pump III to move to neutral.

With fluid trapped in the chamber 3 I, and with the pump ill discharging fluid under pressure into the discharge line I3, pressure will build up in the discharge line ii that is transmitted into the chamber 32.

The pressure-relief valve 45 is adjusted to open in response to a predetermined pressure in the chamber 3! of the cylinder 26, which pressure is occasioned by the pressure of the fluid in the chamber 32 received from the discharge line It. When the pressure in the chamber 32 rises to a value to produce pressure in the chamber 3| to open the pressure-relief valve 45, the piston 25 will be moved in a leftward direction by the pressure in the chamber 32, aided by the spring 3211 which continues the movement initiated by the pressure, the fluid-in the chamber Ii being ex- Q hausted through the pressure-relief valve ll, thus shifting the shift-ring II of the pump ll toward neutral position. The exhausting of the trapped fluid from the chamber II is thus occasioned in response to a predetermined pressure in the discharge line II of the pump Ill. The piston 2| will not move the shift ring I! in a rightward direction to place the pump on discharge stroke after the fluid has been exhausted from the chamber 3| until the valve 40 is againoperated. Any force that is suiilcient to cause a build-up of pressure in the discharge line I: of the pump II that supplies the hydraulic motor ll will cause operation of the control means for the pump il in the aforementioned manner regardless of whether the motor I4 is of the rotary type disclosed in Figure l or of the reciprocating yp Under certain conditions, it may be desirable to shift the pump to neutral before the pressure is reached in the discharge line It at which the control mechanism is set to function, or for emergency reasons it may be desired to cause the in this instance causing the pump it to shift to neutral. The valve 41 can be operated'at any time during the operation of the hydraulic motor It and pump it to quickly discharge the trapping chamber 3I and cause the pump to move to neutral. Also, while the valve 41 may beXoperated as an emergency control for causing the fluid from the trapping chamber ii to exhaust to the tank I 2, it may also be used to cause a shifting of the pump to neutral in response to a predetermined position of the device operated by the hydraulic motor I4. Thus, in the control circuit illustrated in Figure 1, the pump ll can be placed on neutral position either in response to a predetermined pressure in the discharge line of the pump or in response to a predetermined position of a device operated by the motor I4.

From the foregoing description, it will thusbe seen that the operation of a pump to control the discharge of fluid under pressure therefrom can be regulated by placing fluid under pressure in a fluid-trapping chamber for placing the pump on a discharge stroke and thereafter trapping the fluid in the trapping chamber to retain the pump on the discharge stroke. Also, that the pump can be operated to reduce the discharge stroke as occasioned by exhausting the trapped fluid from the trapping chamber in response to a predetermined pressure or in response to the operation of a valve that may be actuated in response to a predetermined position of a device operated by the hydraulic motor.

In Figure 2 there is illustrated the application of the control system to a double-acting hydraulic motor of the type having a diil'erential area piston reciprocable in a cylinder.

In the arrangement illustrated in Figure 2 the hydraulic pump 50 is of the reversible variable delivery type having the service lines 5| and 52 that are interchangeably used for either the pressure or suction-line, depending upon the direction of discharge of hydraulic fluid from the pump 5.. The pump 50 may be of the conventional type using a plurality of radial cylinders that are moved relative to pistons reciprocable therein by means of a shift ring 53 for altering the stroke of the pistons. Pumps of this character are well haown and further description thereof is not deemed necessary. The shift ring 53 is, however, moved from one side of the pump casing to the other to change the direction of flow of hydraulic fluid in the service lines and 52, and when the shift ring 53 is co-axial with the axis of the pump, or the drive shaft of the pump, there will be no discharge of fluid under pressure into either service line 5| or 52, and the pump is on neutral.

The service lines 5| and 52 are adapted to be connected to opposite ends of a hydraulic motor 55 that consists of a cylinder 56 having a piston 51 reciprocable therein as caused by alternate supply and exhaust of hydraulic fluid to opposite ends of the cylinder 56. The piston 51 may have a plunger 58 extending through an end-wall of the cylinder 56 for performing work. It will therefore b seen that the hydraulic motor 55 is provided with a main pressing chamber 59 and a retraction chamber 68 that may alternately receive fluid under pressure from the hydraulic pump 50, depending upon whether the shift ring is on the right or left-hand side of the axial center of the pump.

A shuttle valve 6| having a shuttle member 82 therein is provided between the service lines 5| and 52, and is connected to them by the conduits 53 and 54. The shuttle valve 5| connects with a supply tank 65 by means of a conduit 65 whereby excess fluid from the pressing chamber 59 can be returned to the tank upon a retraction stroke of the piston 51, and fluid can be received into the pump 50 through the shuttle valve 6| when supplying fluid under pressure to the pressing side of the ram during th pressing stroke.

A pressure relief valve 61 is connected to the service line 52 to relieve pressure in this line in a manner that will be hereinafter described.

The shift ring 53 of the pump 58 is moved from one side of the axial center of the pump to the other by means of the plungers 68 and 59 secured to the shift ring 53 and which enter the closed chambers and H respectively. The plunger 68 is of larger diameter than the plunger 69 so that when equal fluid pressure is present in the chambers 19 and T l, the shift ring 53 is moved in a rightward direction.

A pilot pump 12 delivers fluid under pressure into the chamber H through the conduit 13 as received from the tank 65 through the conduit M. An adjustable pressure-relief valve controls the maximum pressure developed by the pilot pump l2, and by-passes excess fluid under pressure through the by-pass line I6.

The pilot pump 12 also supplies fluid under pressure through the conduit TI to the chamber 70 through the conduits I8 and 19. A valve 89 is provided between conduits l1 and 18 to open a passage therebetween when the spool 8| of the valve 80 is moved in a rightward direction against the spring 82 to admit fluid under pressure into the chamber 10 for reasons hereinafter described.

The chamber '18 forms a trapping chamber in which fluid is retained after the chamber is charged for holding the pump 59 on a discharge stroke. the charging of the chamber 18 being occasioned upon opening the valve 88.

Fluid may be exhausted from the chamber 10 either by way of a pressure-operated control member 85 or by Way of a valve member 86. The valve member 85 connects the conduit I9 to the tank 65 by a conduit 81, and has a spool 88 therein urged in a leftward direction by the spring 89 for closing the connection between the conduits.

The control member 85 has a plunger'90 positioned therein for reciprocation in the cylinder bores 9| and 92. The cylinder bore 92 is connected to the fluid-trapping chamber 18 by the conduit 93 while the cylinder bore 9| is connected to the tank by the conduit 94 through an adjustable pressure relief valve. 95 tov permit exhausting of fluid from the cylinder chamber 9|. A conduit 96 connects the conduit 19 from the pilot pump I2 with the conduit 94 to supply fluid under pressure from the pilot pump 12 into the cylinder chamber 9|. A check-valve 91, opening in the direction of the arrow thereon, is provided in the conduit 99 to prevent a return flow of fluid from the cylinder chamber 9|. The cylinder chamber 92 in the pressure control member 85 is connected to the tank 65 by the conduit 99, the reduced-diameter portion 990. of the plunger 90 closing the conduit 99 under certain conditions of operation hereinafter described.

The cylinder chamber 9| of the control member 85 is connected to the service line 5| by means of the conduit I88 whereby fluid under pressure from the service line 5| will enter the cylinder chamber 9| at the right-hand side thereof to cause the plungerv 90 to move in a leftward direction.

The operating conditions of the system illustrated in Figure 2 are such that with the hydraulic pump 50 and the pilot pump 12 operating, pilot pressure will continuously stand in the chamber 1| tending to continuously urge the shift ring 53 in a leftward direction. Assuming that hydraulic fluid has previously exhausted from the chamber 10 and the chamber 9| of the control member 85, the pressure in the chamber 'il will move the shift ring 53 in a leftward direction and the plunger 90 of the control member 85 will stand in the left-hand side of the cylinder chamber 9| with the conduit 99 uncovered by the portion 90a of the plunger 99. The pressure-relief valve 95 has previously been set to open at a value that will establish a predetermined maximum pressure in the service-line 5| when fluid under pressure is supplied to the pressing chamber 59 of the hydraulic chamber 59 of the hydraulic motor 55.

With the pilot pump 12 operating, the spool 8| of the valve 88 is then moved in a rightward direction to open the passage between the conduits l1 and 78 thereby supplying fluid under pressure to the fluid-trapping chamber 19 through the conduit 19 and to the cylinder chamber 9| of the pressure control member through the conduit 96. Fluid under pressure will move the plunger in a rightward direction to close the end of the conduit 99, also fluid under pressure in the chamberlll will cause movement of the shift ring 53 in a rightward direction against the pressure of the fluid in the chamber II to place the pump 50 on a discharge stroke for discharging fluid under pressure through the service line 5|. The valve 80 is then released to close the connection between conduits 11 and 18, thereby trapping fluid in the chamber l0 and in the cylinder chamber 9| of the control member 85. The fluid thus trapped in the chambers will retain the shift ring 53 of the pump 58 in a rightward direction to deliver fluid under pressure into the pressing chamber 59 of the hydraulic motor 55 and withdraw fluid from the retraction chamber 60. Any make-up fluid required for delivery to the pressing chamber 59 by the pump 50 will belaccginplished through the make-up or shuttle va ve The piston 51 of the hydraulic motor 55 will 9 then move through an advancing stroke and build up pressure on work that is to be performed. As the plunger 58 meets resistance, pressure is built up in the chamber 59 that is reflected through the service line 5| in the conduit I and thence to the right-hand, end of the cylinder chamber II. as soon as the pressure on the right-hand face of the plunger 90 builds up to a suflicient value to increase the pressure of the trapped fluid in the left-hand end of the cylinder chamber 9| to the value at which-the relief valve 95 is set, the relief valve will open, thereby permitting the plunger 98 to move in a leftward direction and exhaust fluid from the cylinder chamber 9| through the relief valve 95.

When the plunger portion 90a moves in a leftward direction to uncover the conduit 99, fluid in the chamber 18 will be exhausted through the conduits SI and 90 to the tank 55 thereby permitting the fluid that is standing under pressure in the chamber 1|, as caused by the pilot pump 12, to move the shift ring 58 in a leftward direction to reverse the direction of discharge from the pump 50 from the service line 5| into the service line 52. Once the fluid has been exhausted from the chamber and from the chamber 9| by the aforementioned operation, the pump 50 will remain on reverse stroke until the valve 80 is again actuated to recharge the chambers 10 and iii with fluid under pressure.

with the shift-ring 58 now in the lefthand position, fluid under pressure is delivered through pressure in the service lines I12 and I13. The

time being in an upward position. When the piston 51 bottoms, excess pressure from the pump 59 will be discharged through the pressure relief valve 81 into the tank 85.

From the foregoing operation of the control system illustrated in Figure 2, it will be seen that the double-acting hydraulic motor 55 is carried through a single cycle of reciprocation including forward and reverse strokes, and is automatically reversed when a predetermined pressure is built up on the pressing-side of the piston 51 of the hydraulic motor 55. The foregoing operation of the control system can also be accomplished by a pressure from any other desired source as throughthe line 550 by closing valve 50I in the line I00 and opening valve 502 to the desired pres:

sure source.

The valve 88 in the system disclosed in Figure 2 can perform identically the same functions as the valve 81 disclosed in the system shown in Figure 1, including emergency reversal of the pump at any time during the stroke of operation of the hydraulic motor 55, the reversal of the pump being a complete flow reversal in this instance instead of being to neutral position as previously described. Aiso, the valve 88 can function, like the valve 81, to obtain a reversal of discharge from the pump 58 in response to a predetermined movement or predetermined positionof the plunger 58 of the hydraulic motor 55. Thus, it is possible to provide for both pressure reversal and position reversal of the pump 50 and the hydraulic motor Figure 4 illustrates the use of a trapped fluid for causing reversal of a pump and of a press ram moved by the delivery of fluid from the pump in a manner similar to that disclosed in Figure 2,

service lines I12 and I13 are connected to opposite ends of a hydraulic cylinder I14 in which the press ram I15 reciprocates, the service line I12 serving the pressing chamber I16 of the cylinder I14 and the service line I13 serving the retraction chamber I11. 2

The press ram I15 has a piston I18 on one end thereof reciprocable in the cylinder I14, and the opposite end of the press ram carries a. platen I19.

To provide for rapid traverse of the ram I15 during the down-stroke thereof, and to provide for discharge of excess fluid from the pressingchamber I16 of the cylinder I14 during the upstroke of the ram I15, a surge valve I is positioned in the head of the cylinder I14. Such surge valves are of a well-known type, one of which is disclosed in the patent to Ernst, No. 1,956,758 dated May 1, 1934.

Because of the diflerential area of the piston I 18, make-up fluid is required for the hydraulic system when the pump I10 is delivering fluid into the pressing-chamber I18 through the service line I12, the service line I13 then acting as the suction line for the pump I10. To supply this make-up fluid, the conduit I8I is connected to the retraction or push-back chamber I11 and communicates with a reservoir tank I82. A checkvalve I83 is provided in the conduit I 8| to permit fluid to enter the conduit in the direction of the arrow applied on the check-valve but which prevents discharge of fluid under pressure from the conduit I8I when the pump I10 is delivering fluid under pressure in the push-back chamber I11 for moving the ram I15 upwardly.

To open the surge valve I80 when the ram I15 begins its retraction movement, a conduit I84 connects the conduit I8I with the surge valve I80 whereby to apply pressure upon the surge valve I80 to open the same when fluid under pressure is delivered into the push-back chamber I11.

The hydraulic system thus disclosed in Figure 4 is essentially the closed system, as is the hydraulic system previouly disclosed and described with regard to Figure 2.

The reversing control for the pump I10 consists of a piston I85 that reciprocates in a cylinder I86, thus dividing the cylinder I86 into two chambers I81 and I88. The piston I 85 is connected to the shift ring, or control member I1I by means of a plunger I89. The chamber I81 in the cylinder I86 forms a, fluid-trapping chamber for controlling reversal of the pump I10 in a manner similar to that heretofore described, but which will be described in more detail with reference to the particular structure shown in Figure 4.

A pilot pump I90 delivers fluid under pressure into the conduit I9I as received from the supply tank I92 through the suction line I93. A pressure-relief valve I94 is placed in a by-pass line I95 to discharge fluid from the discharge side of the pump I90 when pressure rises above a predetermined value as controlled by the pressurethat continuously urges the piston in a leftward direction for shifting the control member "I of the pump I in a leftward direction to cause discharge of fluid under pressure through the service line I19.

The fluid-trapping chamber I81 of the cylinder I86 receives fluid under pressure from the pilot pump I90 through the conduit I91 as controlled by a shut-off valve I98 that is constructed in the same manner as the valve members 40, 41, 80 and 86 previously disclosed and described with regard to Figures 1 and 2.

A conduit I99 connects the fluid-trapping chamber I61 with a control member 20. The control member 200 consists of a cylinder having the cylinder chambers 202 and 203 therein that receive the plunger 204 having the reduceddiameter portion 205 that reciprocate in the cylinder chambers 202 and 203, respectively. The conduit I99 connects with the cylinder chamber 203 to permit exhausting of fluid from the fluidtrapping chamber I81 of the control cylinder I86 through the conduits 206 and 201 for return to the tank I92 when the plunger 208 moves in a leftward direction in a manner hereinafter described.

The cylinder chamber 202 connects with the exhaust line 201 by means of a conduit 208 that has a pressure-relief valve 209 therein. The pressure-relief valve 209 is adjustable to control the pressure in the cylinder chamber 202 at which the pressure-relief valve shall open to permit discharge of fluid from the cylinder chamber 202.

The cylinder chamber 202 is supplied with fluid from the pilot pump I90 through the conduit 2 I0 when the valve I98 is opened, the supply of fluid to the chamber 202 being simultaneous with the supply of fluid to the fluid-trapping chamber I81. A check-valve 2 is placed in the conduit 2I0 to isolate the fluid when under pressure in the chamber 202 from the fluid in the trappingchamber I81 during the control operation of the control system in a manner hereinafter described.

A shut-01f valve 2I2 is placed in the conduit 2I3 which connects the fluid-trapping chamber I81 with the tank I92 for quickly exhausting fluid from the fluid-trapping chamber I81 under certain conditions of operation hereinafter described.

Since the flow-controlling member, or shift rin I1I will be moved to the left-hand side of the pump I10, and the piston I85 will be in the left-hand side of the cylinder I86 when fluid is being discharged by the pump through the service line I13 to reciprocate the ram I15, and since mechanism is provided for placing the pump in neutral or no-delivery position when the ram I15 reaches the top of its return stroke, it will be necessary to providefor a make-up of fluid into the fluid-trapping chamber I81 when the piston I85 is moved in a rightward direction when placing the pump in neutral. This can be accomplished through the conduits I99, 206 and 201 because the exhaust passage formed thereby is open.

The mechanism for moving the shift-ring IN to neutral position consists of a rod 2I6 as connected by a link- 2I1 with one end of a bellcrank lever 2I8 that is pivoted upon the pivot 2 I9 carried in a bracket 220 on the press cylinder I14. The opposite end of the bellcrank lever 2I8 is engaged by a collar 22I carried upon the rod 222 that is lifted into engagement with the said end of the bellcrank lever 2I8 when the collar 223 on the rod 222 is engaged by the arm 220 extending from the platen I19. Upward movement of the rod 222 causes clockwise rotation of the bellcrank lever 2I8 about the pivot 2I9 to pull the shift ring I1I of the pump I10 into neutral or no-delivery position wherein the shift ring I1I is co-axial with the pumpin mechanism.

To provide for reversal of the pump I10, that is, to shift the shift-ring from the extreme position on the right-hand side of the pump, the service line I12 that serves the pressing-chamber I16 of the press cylinder I14 is connected to the righthand end of the cylinder chamber 202 in the pressure-control member 200 by the conduit 225. Thus, pressure developed in the service line I12 as a result of resistance met by the ram I15 in producing work is reflected through the conduit 225 to the right-hand end of the plunger 200 to urge the same in a leftward direction.

With the pump I10 in neutral position as shown in Figure 4, the elements of the hydraulic system will be in position as illustrated, and the fluid-trapping chamber I81 will be filled with fluid, but open to exhaust through line 206 as caused by prior movement of plunger 204 to the position illustrated. To place the pump I1 on a discharge stroke to deliver fluid under pressure through the service line I12 into the pressingchamber I16 to start the ram I15 upon a pressing stroke, the valve I98 is opened. Fluid under pressure from the pilot pump I90 will be delivered simultaneously through the conduits I91 and 2 I 0. Delivery of fluid under pressure through the conduit 2I0 to the chamber 202 of the pressure-control member 200 moves the plunger 204 in a rightward direction to close the conduit 206 and thus shut off discharge of fluid from the fluid-trapping chamber I81. The delivery of fluid under pressure into the chamber 202 will thus refill the chamber 202 with hydraulic fluid. The delivery of fluid under pressure into the fluid-trapping chamber I81 of the control member I86 will move the piston I85 in a rightward direction to shift the flow-controlling member I1I of the pump I10 to the right-hand side of the pump and thus place the pump on a discharge stroke for delivering fluid under pressure through the service line I 12. The valve I98 is then released, whereby the valve closes, and fluid is trapped in the fluid-trapping chamber I81 to hold the shift-ring I1I on the right-hand side of the pump against the pressure of the pilot fluid that is standing in the chamber I88 on the righthand side of the piston I85. The fluid in the chamber 202 of the control member 200 is also trapped therein by the check-valve 2H and the pressure relief valve 209.

The ram I15 will thus move downwardly to perform work. As soon as pressure begins to build up in the pressing-chamber I16, the surgevalve I wil1-close so that the desired pressure increase can be obtained in the pressing chamber I16 to perform the desired work. When the pressure in the pressing-chamber I16 builds up to a predetermined value, the pressure thus obtained will be transmitted to the right-hand side of the cylinder chamber 202 in the control member 200 through the conduit 225 thereby increasing the pressure of the fluid in the chamber 202 to the value at which the pressure-relief valve 208 is set to open. Thus, when a predetermined pressure is developed in the pressing chamber I18, the relief-valve 208 will open to allow discharge of fluid from the chamber 202 o! the control member'2l0. The plunger 204 will thus move in a leftward direction causing the reduced-diam- B1161 907E101! 0f the P nger 204 to uncover the end of the conduit 208. When this occurs, fluid from the fluid-trapping chamber I81 of the control member I88 can exhaust through the conduits I88, 208 and 201 to the tank H2. The pilot pressure in the chamber I88 from the pilot pump 0 will then cause the piston I85 to move in a leftward direction and shift the shift-ring I1I from the right-hand side of the pump through neutral to the left-hand side of the pump and thus reverse the direction of discharge of fluid from the pump I from the service line I12 to the service line I13. When the fluid has exhausted from the chamzer 202 of the control member 280 and from the chamber I81 of the control member I86, the shift ring I will remain on the left-hand side of the pump I10 as retained thereby by the pilot fluid present in the chamber in from the pilot pump I90.

with the fluid under pressure discharging through the service line I13, the ram I15 begins an upward movement, or retraction stroke. The pressure in the retraction or push-back chamber in is transmitted through the conduits -I8I and ill to the surge valve I80 to open the same and transmit excess fluid from the pressing chamber I18 to discharge into the tank I82 through the surge valve I80.

The ram I15 will move upward until the arm 220 on the platen I19 strikes the collar 223 on the rod 222 and thus raises the collar 22I intcengagement with the end of the bellcrank lever 2 I8 to rotate the same in a clockwise direction and thus pull the shift ring I1I in a rightward direction until the shift ring places the pumping mechanism in neutral or no-delivery position, at which time fluid will not be discharged through either service line I112 or I18. The pump will remain in neutral position until the valve I98 is again actuated. If, however, fluid should leak from the retraction chamber I11 around the ram 615 the platen I19 will drop slightly to permit counter-clockwise rotation of the bellcrank lever M8 and permit a slight leftward movement of the shift ring ill as caused by the pilot pressure fluid standing in the chamber I88 to again lift the ram I15 to return it to its initial positlon and again place the pump in neutral posi- 'tion.

If it is desired to reverse the movement of the ram E15 at any time during its forward stroke, regardless of the position of the ram or regardless of whether pressure has developed upon the pressing side of the ram, the valve 2I2 may be opened to permit discharge of fluid from the fluid-trapping chamber i8! directly to the tank M2 and immediately shift the pump from full forward discharge stroke to reverse discharge stroke. The valve 2I2 may therefore act as an emergency reverse control.

Figure 6 is essentially the same hydraulic circuit disclosed and described with regard to Figure 4 but with the additional features of full-automatic operation or semi-automatic operation selectively obtained or wherein the ram of the press may-be reversed at the end of its downstroke either in response to a predetermined pressure or in response to a predetermined position each of which is selectively controlled, and in- 14 cludes the further feature or an automatic slowdown of the ram near the end of its forward stroke.

The elements or the system shown in Figure 6 that are identical with the elements of the system illustrated in Figure 4 will thus be identified by the same numeral as occurs in Figure 4 but with the sumx a. In so far as the operation of the apparatus disclosed in Figure 6 is concerned with the elements that are identical with the elements in Figure 4, the functioning of the system and controls thereof is identical to that previously disclosed and described with regard to the system shown in Figure 4. The only exception is that when the pump I is moved to neutral position at the end of the retraction stroke, the make-up fluid for the fluid-trapping chamber I81a flows through the check-valve 228 placed in the bypass line 221 between the exhaust line 208a and the conduit I91a that connects with the fluidtrapping chamber I81a. The reason for the check-valve 228 is that when the ram II5a of the press is to be reversed solely in response to the position of the platen, the valve 228 in the pressure line 225a is closed to thereby isolate the pressure control member 200:; from the rest of the system. The plunger 280:: will therefore at this time be in a right-hand position as illustrated in Figure 6 to shut off the passage 208a so that the make-up of fluid to the fluid-trapping chamber I81a could not occur through the conduit 208a as previously described with regard to Figure 4.

The additional elements of the system that provide for full automatic operation of the press, reversal of the ram of the press at a predetermined position in the forward stroke thereof and a slow-down operation in the forward stroke of the press, consist of the spring-actuated valves 230 and 23I and a control cylinder 232.

The spring-actuated valve 238 is similar in all respects to the spring-actuated valves 50, 41, 88 and 88 previously described with regard to Figure 1. In place of being manually operated, however, the valve 230 is opened by a cam 233 that is carried upon an arm 238 extending from the platen 519a of the press. The spring-actuated valve 230 is connected in parallel with. the valve I880. by the conduits 235 and 238 so that either valve IBM or 230 can supply fluid under pressure into the fluid-trapping chamber I81a to shift the shiftring I1Ia of the pump I10a to the right to place the pump on stroke for delivery of fluid under pressure into the service line 1121:. A manuallyoperated shut-off valve 231 is placed in the conduit 235 to prevent flow of fluid through the valve 230 if it is not desired that the same shall effect operation of the hydraulic system. The

valve 230 is therefore the means for restarting a downward movement of the ram a of the press upon return to the top of its retraction stroke, and therefore provides for full automatic operation of the press.

The valve 28I is identical-with the valve 231! and may be operated by the same cam 233, or if desired, a separate. cam can be used to actuate the valve 23f. The valve 23I is to be actuated by the cam 233 when the platen 118a of the press reaches the end of its down-stroke and completes the pressing operation upon the desired work. The valve 23I is connected hydraulically in paralel with the valve 2I2a by the conduits 238 and 239 so, that either valve 23I or 2I2a can directly exhaust fluid from the fluid-trapping chamber I81a into the tank I924: regardless of the funcautomatically reversed and placed on a retraction stroke, this being entirely independent of the operation of the pressure-control member 200a which also places the ram !'!5a on a return stroke when a redetermined pressure builds up in the pressing-chamber Vita in the manner as heretofore described with regard to the apparatus illustrated in Figure 4.

If manually-operated valves 23? and 240 are closed and the valve 228 is open, the control system for the pump l'llla will function in identically the same manner as previously described with regard to Figure 4 on a semi-automatic operating cycle with the ram Hta being reversed at the bottom of its stroke in response to a predetermined pressure developed in the pressingchamber I'lBa.

If it is desired to operate the press on a fullautomatic cycle of operation, the valve 231 will be opened. With the control system arranged in this manner, the press will be reversed at the bottom of its stroke in response to a predetermined pressure as before, or when the platen H911 approaches the top of its stroke, and before thearm 224a on the platen has engaged the collar 223 on the rod 222a to shift the shift-ring IHa to neutral, the cam 233 will open the valve 230 to permit pilot fluid under pressure to flow through the conduits 236 and-235 into the fluid-trapping chamber !8!a and into the cylinder chamber 202a of the pressure-control member 230a to thereby shift the shift-ring Ha of the pump "0a to the right and again place the pump on a discharge stroke for delivering fluid under pressure through the service lines I12a for delivering fluid to the pressing-chamber !!6a of the press.

If it is desired to operate the press to reverse the platen at a predetermined position of its forward stroke regardless of the pressure that is built up in the pressing chamber "6a, the valve 228 is closed, thus isolating the pressure control member 200a and the valve 240 is opened to place the valve 23! in an active circuit. Thus, when the platen ll9a reaches a predetermined posi--- tion in its forward stroke, the cam 233 will open the valve 23! to permit discharge of fluid from the fluid-trapping chamber !8'!a directly to the tank I92 through the valve 23!, whereby the pilot fluid under pressure in the chamber !88a will shift the shift-ring IT! a to the left and reverse the direction of discharge of fluid from the pump !!3a to deliver the fluid into the service line l'!3a.

If it is desired to reverse the platen l19a at a predetermined position in its stroke of forward movement, but to provide a safety pressure control in case the pressure in the pressing chamber llfia should rise to a dangerous degree, both valves 24!] and 228 can be opened to place both control devices in an active circuit.

Under certain conditions of operation of the hydraulic press, particularly when the press is provided with a rapid traverse system for causing rapid approach of the forming dies upon the work, it is desirable to slow down the forward movement of the ram until the work has been 16 engaged. Thereafter, the movement of the ram can either be retained at the slow forward speed or can again be speeded up to perform the work operation.

The slow-down control cylinder 232 has a piston 24! movable in a cylinder bore 242. The cylinder 232 is connected to the fluid-trapping chamber l8ia of the control cylinder l86a secured to the pump I'Hla by means of the conduit 243. The piston 24! thus establishes a closing end-wall in the cylinder 242 to provide a sealed chamber 245 that is in direct hydraulic communication with the fluid-trapping chamber l8la. The piston 24! has an actuating-rod 246 extending through a wall of the slow-down control member 232 engaging a slide 241.

The slide 24'! has a surface 248 that normally retains the piston 24! in'position as shown in Figure 6 thereby establishing a definite total volume in the fluid-trapping chamber l87a, the chamber 245 of the control member 232 and the associated conduits. As long as the piston 24H does not move within the cylinder 242, the slowdown control member 232 will have no influence upon the operation of the control system. However, the slide 24! is provided with a recessed surface 249 that permits the actuating member 246 to move in a rightward direction and thus move the piston 24! n'ghtwardly to increase the volume of the chamber 245 in'the slow-down control member 232. The recessed surface 249 is enaged by the actuating member 246 of the slow.. down control member 232 during the forward movement of the ram "5a, and preferably just before the work is engaged by the ram. Since pilot pump pressure stands continuously in the chamber !88a of the control member mm, the increase in total volume in the hydraulic system directly associated with the fluid-trapping chamber !8!a will permit movement of the piston !a in a leftward direction in proportion to the increase in volume in the hydraulic system associated with the fluid-trapping chamber I81a. This movement of the piston I85 will move the shift-ring IHa, in a leftward direction toward neutral position and thereby reduce the delivcry of the pump I'lDa into the service line !'!2a to reduce the rate of forward movement of the ram !'!5a.

If it is desired to continue the movement of the ram at the reduced speed, the recessed surface 249 will be of suflicient length to retain the piston 24! in the newly advanced position until the stroke of the ram !'!5a is complete. However, if it is desired to again speed up the ram "5a after the work is engaged, the slide 24'! can be provided with a raised surface 250 which causes the piston 24! to move in a leftward direction when the actuator 246 engages the surface 250. The fluid will be displaced from the chamber 245 of the slow-down control 232 by this movement and return the piston I85 to its original position by moving the same in a rightward direction.

It will, of course, be understood that the illustration of the slide and the cam surfaces associated therewith for operating the slow-down control member 232 are merely shown in diagrammatic form and that these surfaces can be made of any length or can be adjustable to change the point at which the slow-down occurs or change the rate of forward movement of the ram after the slow-down occurs. Also, the cam 233 for engaging the valves 23!! and 23! may also the valves 230 and 231 are actuated be fully adjustable to control the nt-atwhich is very similar to the control systems heretofore disclosed, in its operation. However, in the system illustrated in Figure there is shown the feature of a high-pressure release for relieving the pressure in the pressing-chamber of the ram immediately after the pressing stroke is complete, associated with a pump by-pass control that bypasses the pump until the pressure of the pressing-side of the rain has decayed sufllciently to permit the rain to start on an upward stroke, whereupon the pump by-pass is closed and the ram can begin its upward or retraction stroke.

In Figure 5 the hydraulic circuit between the pump 255 and the cylinder255 of the hydraulic press is of the same general closed type of circult heretofore described with regard to Figures 4 and 6 wherein the pump 255 is of the reversible variable delivery type. The pump 255 delivers hydraulic fluid under pressure alternately into the service lines 251 and 258 to opposite ends of the hydraulic cylinder 256. The piston 259 reciprocates in the cylinder 258 and carries the ram plunger 260 for retraction thereby. The cylinder 256 has the pressing chamber 261 and the retraction chamber 252. A surge valve 263 is associated with the pressing chamber 261, and a make-up line 268 connects the retraction chainber 2622 with the tank 265, and has a check-valve 265 therein.

The shift ring 261 of the pump 255 has a plunger 258 secured on one side thereof having a piston 269 that reciprocates in the control cylinder 210 to divide the control cylinder into a fluid-trapping chamber 211 and a chamber 212. The chamber 212 is connected to a pilot pump 213 by a conduit 218, which pilot pump receives fluid from 40 the tank 215 through the conduit 216, and excess pilot fluid-is relieved through the pressure relief valve 233a to the tank 215. The pilot pump pressure in the chamber 212 continuously urges the shift the shift ring 261 to the right to place the pump on discharge stroke to deliver fluid under pressure into the service line 258.

A plunger 211 extends between the piston 269 and one end of the bellcrank lever 218 that is under pressure through the conduit 285 under 0 control of the spring-actuated valve 286 when the valve 286 is open. A check-valve 281 is placed in the conduit 285 between the valve 286 and the control cylinder 210 to prevent pressure from the fluid-trapping chamber 211 from being trans- 5 mitted below the check-valve 281 in the conduit 285. Aconduit 288 connects the conduit 285 above the check-valve 281 with a pressure-control member 290, and particularly with the cylinder chamber 291 provided in the control member 290. A plunger 292 reciprocates in the control member 290 within the cylinder chamber 293, the control member 290 functioning in all respects the same as the control members 85, 200

and 200a previously described. The cylinder piston 269 in a rightward direction, tending to 45 the rod 281 up- 55 chamber 293 of the control member 290 is connected to the tank 215 by the conduit 294 that has the pressure-relief valve 295 therein for relieving pressure of a predetermined valve from the chamber 293. A conduit 296 connects the cylinder chamber 291 of the control member 299 with the exhaust conduit 294, permitting discharge of fluid from the fluid-trapping chamber 211 of the control member 210 through the chainber 291 of the control member 2911.

A conduit 291 connects the chamber 293 of the control member 290 with the conduit 285 between the check-valve 281 and the valve 286 to introduce fluid into the chamber 293 and refill the same after operation of the control member 298.

A spring-actuated valve 298 is connected to the exhaust conduit 290 by the conduit 299 to quickly exhaust fluidfrom the fluid-trapping chamber 211 in the same manner as the operation of the valves 41, 86, 212 and 212a heretofore described. Also, by actuating the valve 298 by a cam 300 on the platen 282, the valve 298 may perform the function of position reversal for the platen 282 of the press in the same manner as heretofore described with regard to valve 23! illustrated in Figure 6.

The shiftring 261 of the pump 255 has a plunger 301 extending therefrom that moves in a cylinder 382. The cylinder 302 has the chamber 303 therein connected to the service line 251 by the conduit 30d whereby the pressure in the service line 251 is also present in the chamber 303. The cylinder 302 is connected to the supply tank 265 by a conduit 305 which is opened by the piston 301 when moved in a rightward direction to place the shift ring on the right-hand side of the pump 255 for delivery of fluid into the service line 258.

The service line 258 is connected to the tank 265 by a by-pass line 306 and the line 305 through a by-pass valve 301 that has the spool 3118 there in spring-pressed in the left-hand direction by the spring 309 to normally close the by-pass line 306'. A piston 310 in the valve 301 engages the spool 308 and urges the same in a right-hand direction when pressure is present in the conduit 305 that is transmitted against the piston by the conduit 311.

With the pump 255 in neutral position as illustrated in Figure 5, the valve 286 is opened to supply pilot pump pressure into the fluid-trapping chamber 211 to shift the shift-ring 261 in a leftward direction and place the pump 255 on a discharge stroke for delivering fluid under pressure into the service line 251. Simultaneously, fluid is delivered through the conduit 291 for refilling the chamber 293 in the control member 290 which moves the plunger 292 in a leftward direction to close the exhaust passage 296. The ram 260 then starts on a downward movement.

When the ram meets resistance and pressure is built up in the pressing chamber 261 by the pump 255, the pressure is transmitted through the conduit 304 in the chamber 303 of the control cylinder 302 thereby producing pressure in the fluid-trapping chamber 211 of the control cylinder 210 that is transmitted to the cylinder chamber 291 of the control member 290 to develop pressure in the chamber 293 of the control member 290 and thereby open the pressure-relief valve 295 to permit discharge of fluid from the chamber 293 of the control member 290. This discharge of fluid permits the plunger 292 to move in a rightward direction and open the by-pass line 296 which thereby permits fluid to discharge from the fluid-trapping chamber 2" of the control cylinder 210, and thus pressure in the chamber 303 against the piston plunger 30l will move the shift ring 261 of the pump 255 in a rightward direction to exhaust fluid from the fluid-trapping chamber 2" and shift the pump toward reverse stroke. With the control plunger 292 unable to return to its initial position due to exhaust of fluid from chamber 233, the pilot pump pressure continuously standing in the chamber 212 will continue the movement of the shift ring 261, fluid from chamber 21l freely exhausting through lines 288 and 234, so as to reverse the discharge of fluid under pressure into the service line 258.

When high pressure is developed in the pressing chamber 26l of the pressing cylinder 256, the pressure holds the surge valve 263 closed until the pressure in the pressing chamber 26l can be relieved sufliciently to permit the pushback pressure in the chamber 262 to open the surge valve 263. The release of the pressure from the pressing chamber 26! must therefore occur before the full pump discharge is delivered into the push-back chamber 262 of the press cylinder to avoid shock in the press. For this purpose, the piston 30l of the control member 302 uncovers the exhaust conduit 305 to permit a release of the high pressure into the supply tank 265. Simultaneously, however, the pressure in the conduit 305, transmitted through the conduit 311 against the piston 3I0 moves the spool 308 of the valve 301 to the right to open the by-pass line 306 and thereby permit the pump 255 to discharge directly to the tank 265. A resistance valve 3l2, that is adjustable, is placed in the exhaust line 305 between the line 3 and the tank 265 toinsure operation of-the by-pass valve 301 before the pump 255 completely reverses the direction of discharge of fluid for delivery into the service line 258.

As soon as the pressure in the pressing chamber 26l has decayed to a sufllcientiy low value, the spring 303 in the by-pass valve 301 will shift the spool to the left and close the by-pass line 306, whereafter the pump 255 will deliver fluid under pressure into the service line 256 to begin the retraction stroke of the ram 260.

In Figure 3 there is illustrated the application of the use of trapped fluid for controlling operation of a hydraulic pump of the self-centering type to place the same on neutral position when a predetermined pressure is developed in the discharge line of the pump.

In the arrangement illustrated in Figure 3, the pump 320 has a shift-ring 32l for controlling the discharge of the pump into the service lines 322 and 323. The pump may be of the wellknown radial type heretofore referred to so that it has a variable capacity and is reversible in its direction of discharge of fluid under pressure.

To obtain the self-centering feature in the 20 check-valve 331 therein that opens in the direction of the arrow applied on the valve.

A pressure control member 340 is provided with a plunger 34l that has the reduced-diameter portion 342, the plunger and the reduced-diameter portion thereof reciprocating in the cylinder chambers 343 and 344, respectively. A Spring 345 normally urges the plunger 34! in'a rightward direction as shown in Figure 3.

A pilot pump 346 receives fluid from a supply tank 341 through the conduit 343 and discharges the fluid into the conduit 343. A pressure-relief valve 350 is placed in a by-pass line 35I to retain the pressure on the discharge side of the pilot pump 346 at a predetermined and relatively constant value. A spring-actuated valve 352 having a spool 353 therein controls the flow of fluid under pressure into the conduit 354 that connects with the cylinder 326, and also controls exhaust of fluid from the cylinder 321 through the conduits 355 and 356 into the exhaust line 351.

A similar spring-actuated valve 360 having a spool 36| controls flow of fluid under pressure into the cylinder 321 through the conduits 356 and 355 and simultaneously controls exhaust of fluid from the cylinder 326 through the conduits 354, 362 and 363 into the exhaust line 351.

A pressure-relief valve 365 connects the chamber 343 of the control member 340 with the exhaust line 366 to permit exhaust of fluid from the control member 340 when fluid under pressure is supplied to the chamber 344 thereof during operation of the pump 320.

A conduit 361 connects the chamber 344 of the control member 340 with the exhaust line 366 to permit discharge of fluid from the cylinder 326 under conditions of operation hereinafter described. A check-valve 365 is connected between I the conduit 361 and. the chamber 343 of the control member 340 to supplyfluid to the chamber 343 and refill the same under certain conditions of operation of the system.

With the hydraulic pump 320 being positioned on neutral, as shown in Figure 3, the valve 352 is actuated to open the conduits 354 and 356 whereby pilot pump fluid is supplied to the cylin der chamber 326 to urge the shift-ring in a rightward direction and thus place the pump on stroke for discharge of fluid under pressure through the pump, the shift ring 32! has attached thereto plungers 324 and 325 on opposite sides thereof that extend into the control cylinders 326 and 321, respectively. Springs 323 and 323 engage the perforated washers 330 and 331 which respectively engage the plunger-s 324 and 325. The

springs 323 and 323 hold the washers 330 and 33! against the shoulders 332 and 333 in the respective cylinders to retain the pump in neutral or no-delivery position. The stroke of the pump on either side of neutral is regulated by the adlusting screws 334 and 335.

The service line 322 is hydraulically connected to the cylinder 321 by the conduit 335, and has a service line 322. The valve 352 is then closed thereby trapping fluid in the cylinder chamber 326. When pressure builds up in the service line 322, the pressure is transmitted through the conduit 336 into the cylinder chamber 321 thereby working on the end or the piston plunger 326 to move the shift ring 32l in a leftward direction. When the pressure rises to a predetermined value, the pressure developed in the cylinder chamber 326 will be transmitted to the chamber 344 of the control member 340 to increase the pressure of fluid in the chamber 343 and thereby exhaust the same through the relief valve 365 and permit the shift-ring 32l to move in a leftward direction. Because the pressures in both chambers 326 and 321 are substantially equal, the shift-ring 32l will move to neutral position and there stop.

To reverse the direction oi flow of fluid from the pump 320, the valve 360 may be actuated to supply fluid from the pilot pump 346 to the cylinder chamber 321 and shift the shift-ring 32! in a leftward direction. When the device operated by the delivery of fluid through the service line 323 approaches the end of its stroke of operation the valve 310, which is a spring-actuated valve, will be operated to connect the conduits 21 332 and 393 to the exhaust line 331, thereby rehaving all measure in the cylinder chambers 329 and 321 to permit the centering springs 329 and. 329 to move the pump to neutral position.

In Figure 7 there is illustrated the control system of this-invention as applied to the operation of a 4-way valve for controlling the direction of flow of fluid from a hydraulic pump to opposite ends of a, hydraulic motor, the pump being of the uni-directional discharge type.

In the arrangement shown in Figure 7 the hydraulic press consists of a cylinder 311 that receives a piston 312 having a ram 313 thereon for reciprocating the platen 314. The hydraulic pump 315 receives fluid from the supply tank 319 through the conduit 311, and discharges fluid under pressure into the conduit 313 that is connected to a 4-way flow control valve 390. The 4-way valve has the service lines 391 and 392 connected thereto for supplying fluid under pressure to opposite ends of the cylinder 31! to serve the pressing chamber 393 and the retraction or pushback chamber 394. A spool 395 having the piston heads 399 and 391 thereon is positioned within the'4-way valve 390 to alternately connect the supply line 319 with the service lines 391 and 335. Exhaust lines 399 and 399 are also connected to the 4-way valve for alternate connection with the service lines 39l and 332 upon movement of the spool 395 in the 4-way valve 390.

The pump 315 may be of the uni-directional variable dellvery type having a pressure control mechanisn for shifting the pump to neutral when a predetermined pressure exists in the discharge side of the pump, or a pressure relief valve can be provided for by passing the flow from the pump to maintain a pressure on the discharge side of the pump not greater than a predetermined maximum pressure.

The 4-way valve 399 has a cylinder chamber 399 associated therewith that receives a piston 391 that is directly connected to the piston 391 of the spool 395 by the rod 392.

The piston-head 39l divides the cylinder chamber 390 into two chambers 393 and 394. The chamber 393 is constantly in communication with the discharge side of the pilot pump 39! by means of the conduit 399 whereby the fluid under pressure in the chamber 393 constantly urges the piston 391 downwardly to position the 4-way valve spool 395 in the position as shown in Figure '7. The chamber 394 of the cylinder 390 is connected with the pilot pump 395 by a conduit 391 and the flow of fluid through the conduit 391 is regulated by a spring-actuated valve 399 identical with the valves 49 and 41 heretofore referred to. A pressure relief valve 399 is provided in the by-pass line 400 to by-pass excess delivery of fluid from the pilot pump 395 and maintain a relatively constant pressure on the discharge side of the pump.

A messure-control member 405 is connected to the cylinder chamber 390 and has a piston 40l therein that carries a plunger 402 as an integral part thereof. The control member 405 has a fluid-trapping chamber 403 that is provided with a presure relief valve 404 thereon to relieve pressure in the chamber 403 upon operation of the valve as hereinafter referred to. The reliefvalve 404 is connected with the tank 319 by an exhaust line 409, and the plunger 402 is adapted to imcover an exhaust line 401 upon operation of the control member 40!.

Pressure for operating the control member 405 is developed in the chamber 499 as conducted thereto by the conduit 499 from the service line 331 that connects with the chamber 393 of the hydraulic cylinder 3". A plunger member 0 extends from within the chamber 409 into engagement with the 4-way valve spool 339 to move the same downwardlywhen pressure is developed in the chamber 403.

a for operation of the device as hereinafter described. A check-valve 412 is placed in the conduit 4 to prevent escape of fluid under pressure from the chamber 403.

A spring-actuated valve "3 is provided in the by-pass line 4 to provide a quick release of fluid from the fluid-trappin chamber 394 to cause reversal of the flow of fluid to the cylinder 3" at any time during the forward motion thereof. V

The operation of the system disclosed in Figure '1 is similar in all respects to the operation of the systems heretofore described except that a 4-way valve is shifted to change the direction of flow from a uni-directional pump in place of shifting the flow-controlling member of a variable delivery pump.

To start the operation of the ram 313' the valve 393 is opened to supply fluid under pressure into the chamber 394 which lifts the spool 395 of the 4-way valve to connect the supply line 319 with the service line 3". The valve 398 is then closed and the fluid istrapped'dn the chamber 394. The press ram 313 then moves on a down-stroke.

' When pressure builds up in the pressing chamber 393, the pressure is transmitted through the conduit 409 into the chamber 409 to act upon the plunger 0 and urge the spool 385 of the 4-way valve 380 downwardly. This pressure on the plunger 0 .thus develops pressure in the fluid in the trapping chamber 394 which in turn is transferred to the plunger 402 to develop pressure in the fluid contained in the chamber 403 which is relieved or exhausted through the pressure-relief valve 404. Thus; a predetermined pressure in the pressing chamber 383 will cause exhausting of fluid from the chamber 403 and permit the valve spool 385 to move downwardly together with the piston 401 until the plunger 402 uncovers the exhaust line 401, at which time the ;fluid in the trapping-chamber 394 will exhaust to the tank 316 through the lines 401 and 409 and the spool 395 will be permitted full movement downwardlyto now connect the supply line 318 with the service line 392 to place the ram 313 on a'retraction stroke. When the ram 313 arrives at the top of its retraction stroke, the piston 311 may uncover a conduit 5 to permit by-passing of the fluid from the push-back chamber 394 through the conduits 5. 3M and 398 to exhaust, thus stopping the press ram at the upper end of its stroke.

The press ram 313 is thus reversed in response to a predetermined pressure on the pressing side of the ram as developed during work-stroke of the ram.

If it is desired to reverse the movement of the press ram in response to a predetermined position, acam 416 carried by the platen 314 may engage the operating member of the valve 413 when the platen 314 arrives at a predetermined position in its delivery stroke to release the fluid from the trapping chamber 394 and thereby permit reversal of the flow of fluid through the 23 4-way valve 330 to initiate a retraction stroke of the ram.

If it is desired to make the press fully automatic, instead of semi-au matlc as previously described, a cam 4i'l carri by the platen 314 may engage thevalve 333 to open the same before the piston 312 of the ram 313 uncovers the conduit 5 and thereby restart the ram on another downward stroke in the same manner as heretofore described with regard to the manual operation of the valve 393.

The pressure relief valves that have been heretofore referred to during the description of the various movements of the system of this invention for relieving the pressure fluid may be of the conventional spring-control type wherein a spring opposes the operation of a valve member to retain the valve member closed until a predetermined pressure is reached in the control valve for opposing the action of the spring and thus open the valve member. Such valves are well known and further description thereof is not believed necessary.

Figure 8 illustrates a modified form of control valve that can be used in place of the valves of the type illustrated in Figure 1 by the valves 40 and 41. In the arrangement illustrated in Figure 8 the valve consists of a body 4| 8 having a valve member 4!!! therein that is received on a stem 420. Aspring 42l retained between the end-wall 422 of the body and a collar 423 on the stem 420 urges the valve 9 upon its seat 424 to close the passage between the service chambers 425 and 426. A suitable push-button 421 can be provided for opening the valve 9 to place the service chambers 425 and 426 into communication.

In Figure 9 there is illustrated a slightly modifled arrangement of the pressure control member that regulates the release of fluid from the trapping-chamber to permit reversal of the pump. In this arrangement the pressure control member 43!! consists of a plunger 43! that has a reduced chamber portion 432, the plunger being reciprocable in the cylinder bores 433 and 434.

The cylinder bore 434 has attached thereto a disclosed. The pressure of the fluid in the fluid-trapping chamber 440 urges the piston 43l leftwardly to exhaust fluid from the chamber 434 through the relief-valve 435 until the piston 43! uncovers the exhaust line 4 to permit escape of fluid from the fluid-trapping chamber 440 and thereby permit freedom of movement of the piston 438 in a leftward direction in the manner heretofore described.

While the apparatus disclosed and described herein constitutes preferable forms of the invention, yet it will be understood that various alterations can be performed with regard to the manner in which the elements of the hydraulic system are interconnected and in the structure of the various elements without departing from the spirit 24 of the invention, and all modifications that fall within the scope of the appended claims are in tended to be included herein.

' I claim:

1. A control mechanism adapted to be operatively connected to a hydraulic system that includes a' pump hydraulically connected to a hydraulic motor; said mechanism including a flowcontrolling member for changing the delivery of fluid under pressure from the pump, means forming a chamber to retain fluid therein, a member positioned within said chamber that is operably connected to said flow-controlling member for movement therewith, means for supplying fluid under pressure into said chamber to move said flow-controlling member in one direction to establish delivery of fluid under pressure from thepump, means for trappin the fluid in the said chamber, means for urging said member in said chamber in an opposite direction of movement to the aforementioned direction of movement of said flow-controlling member to place said trappedfluid under pressure and to change the delivery of fluid under pressure from the pump upon release of the trapped fluid from the chamber, means forming a second chamber to retain fluid therein and having movable means therein, means providing a fluid connection between said flrst and second chambers, means operably associated with said second chamber for entrapping fluid therein upon delivery thereof into the secand chamber and for releasing the entrapped fluid from said second chamber to permit movement of said member therein with concurrent movement of said flow-controlling member to change the delivery from the pump.

2. A control mechanism adapted to be operatively connected to a hydraulic system that includes a pump hydraulically connected to a hydraulic motor; said mechanism including a flowcontrollin member for changing the delivery of fluid under pressure from the pump, means forming a chamber to retain fluid therein, a member positioned within said chamber that is operably connected to said flow-controlling member for movement therewith, means for supplying fluid under pressure into said chamber to move said flow-controlling member'in one direction to establish delivery of fluid under pressure from the pump, means for urging said member in said chamber in an opposite direction of movement to the aforementioned direction of movement of said flow-controlling member to change the delivery of fluid under pressure from the pump, means forming a second chamber to retain fluid therein having a movable member therein, means providing a fluid connection between said first and second chambers, means operably associated with said second chamber for entrapping fluid therein upon delivery thereof into the chamber and responsive to the pressure in the discharge side of the pump for releasin the entrapped fluid in said chamber to permit movement of said member therein with concurrent movement of said flow-controlling member to change the delivery from the pump.

3. In a control mechanism for a hydraulic sys- 25 motor in one direction; means for urging said member against said trapped fluid toward position to reverse the delivery oi fluid to said motor; a second fluid operable means hydraulically connected to said flrst operable means for regulating the action thereof; means associated with said second fluid operable means for entrapping fluid therein and including pressure responsive-means for releasing the entrapped fluid to permit actuation of second fluid operable means with concurrent movement oi said flow-controlling memher to reverse the delivery of fluid to said motor; and means for conducting fluid under pressure from the discharge side of the pump for application on said second fluid operable means for causing exhaust of fluid therefrom to permit the said movement of said flow-controlling member.

a. In a control mechanism for a hydraulic system including a fluid source and a motor connected to receive fluid therefrom and a flow-controlling member movable for reversibly controlling the delivery of fluid to the motor, a chamber, means movable in said chamber partitioning the same into two compartments and connected with said flow-controlling member for movement therewith, means for supplying fluid under pressure to one of said compartments for actuating said movable means to shift said flow-controllin member in ;one direction, means for entrapping the fluid in the said compartment including pressure relief means, and means connecting the other said compartment with the pressure side of said motor whereby a predetermined pressure therein of the pump will develop suflicient pressure in the first mentioned compartment to actuate said relief means.

5. In a control mechanism for a hydraulic system including a pump and a motor hydraulically interconnected and relatively variable in capacity; a flow-controlling member for changing the relative capacities of said pump and motor; a chamher, and means connected with said member and movable in-said chamber and partitioning the same into two compartments; means for momeny tarily supplying fluid under pressure into one of said compartments for moving said movable means to shift said flow-controlling member in one direction; means entrapping the fluid in the same compartment including pressure relief means responsive to a predetermined pressure in the said compartment for exhaustin fluid therefrom; means for delivering fluid under pressure from the discharge side of the pump into the other of said compartments to cause said predetermined pressure to be built up in the first mentioned compartment and thereby upon said relief means to actuate the latter and cause movement of said flow-controlling member in the other direction. and means operable independently of said relief means and irrespective of pressure on the discharge side of the pump for exhausting entrapped fluid from said chamber to bring about movement of said flow-controlling member in the other direction.

6. An hydraulic control mechanism for a hydraulic system that includes a pump hydraulically connected to a hydraulic motor and adapted to have the delivery of fluid therefrom reversed to\ the hydraulic motor; the control mechanism including a flow-controlling member for reversing the delivery of fluid from the pump to the hydraulic motor, fluid operable flow controlling means operably connected to said flow-controlling member for actuation thereof. means for temporarily delivering fluid under pressure to said flow controlling means to charge the same with fluid under pressure for moving said flowcontrolling member in one direction to direct the fluid under pressure from the pump to the hydraulic the delivery of fluid from the draulic motor,

trolling means to motor in one direction, means for continuously urging said flow-controlling member in an opposite direction against the'action of said fluid pressure to reverse the direction at flow of fluid from the pump to the hydraulic motor, fluid operable means hydraulically connected with said flow controlling means to entrap the said fluid therein after supply thereof into the chamber to prevent said last mentioned means from moving said flowcontrolling member and actuated-by fluid pres=- sure to release the entrapped .fluid to permit movement of saidflow controlling means, and separate means for releasing the entrapped fluid from said flow controlling means to permit movement of said flow-controlling member in the said opposite direction. I

7. An hydraulic control mechanism for a hydraulic system that includes a pump hydraulically connected to a hydraulic motor and adapted to have the delivery 01' fifiii'd therefrom reversed to the hydraulic motor; the control mechanism including a flow-controlling member for reversing the delivery of fluid from the pump to the hydraulic motor, fluid operable flow controlling means operably' connected to said flow-control-' ling member for actuation thereof, means for temporarily delivering fluid under pressure to said flow controlling means to charge the same with fluid under pressure for moving said flow-controlling member in one direction to direct the fluid under pressure from the pump to the hydraulic motor in onedirection. means for continuously urging said flow-controlling member in an opposite direction against the action 0! said fluid pressure to reverse the direction at flow of fluid from the pump to the hydraulic motor, fluid operable means hydraulically connected with said flow controlling means to entrap the said fluid therein after the said supply thereto to prevent said last mentioned means rrom moving said flow-controlling member and including fluid operated means responsive to pressure in the discharge side of the pump to operate said fluid operable means for releasing the entrapped fluid from controlling means to permit movement of said flow-controlling member in the said opposite direction.

8. An hydraulic control mechanism for a hydraulic system that includes a pump hydraulically connected to a hydraulic motor and adapted to have the delivery of fluid therefrom reversed to the hydraulic motor; the control mechanism including a flow-controlling member for reversing pump to the hyfluid operable flow controlling means operably connected to said flow-controlling member for actuation thereof. means for temporarily delivering fluid under pressure to said flow controlling means to charge the same with fluid under pressure for moving said flow-controls.

ling. member in one directionto direct the fluidunder pressure from the pump "to the hydraulic urging said flow-controlling member in an opposite direction against the action of said fluid pressure to reverse the directlonoi flow of fluid from the pump to the hydraulic motor; fluid operable means hydraulically connected with said flow conentrap the said fluid therein after the said supply thereto and actuated by fluid pressure to release the entrapped fluid to permit movement of said flow controlling means and member and including relief means operable in response to a predetermined pressure in said second fluid operable means to prevent the same from allowing movement of said flow-controlling member, and means hydraulically connecting the discharge side of said pump with said secondhydraulically connected to a double acting hydraulic motor for advancing and retracting th ram' of the motor, a flow-controlling member for reversing the direction of delivery of the fluid under pressure from the pump to the motor, first fluid operable means operably connected to said flow-controlling member for actuation thereof.

and adapted to receive fluid under pressure for moving said flow-controlling member in one direction to cause delivery of fluid from said pump to the advancing side of said motor, means for entrapping the said fluid in said fluid operable means to retain said flow-controlling member in said position, second fluid operable means acting in opposition to the first mentioned fluid operable means and continuously urging said flow controlling member in the opposite direction to reverse the direction of flow of fluid under pressure and deliver the same to the retraction side of the motor, valve means connected between said first fluid operable means and exhaust and connected to be actuated by the pressure developed in the pressing side of the motor for releasing the trappedfluid to permit the said movement of the flow-controlling member to reverse the movement of said motor, and other means connected in parallel with said valve means operable to release the trapped fluid independently of and irrespective of the pressure on the pressing side of the motor.

10. In combination, a. hydraulic motor including reciprocable ram means; a reversible discharge pump; means forming a hydraulic circuit between said pump and said hydraulic motor for reciprocating said ram means in both directions; and an hydraulic control means for reversing the direction of flow of fluid from said pump to said motor for reciprocating said ram; said control means including fluid operable means for actuating said pump to cause discharge therefrom in one direction, a second fluid operable means hydraulically connected with said first fluid operable means for governing the action thereof, means for momentarily supplying fluid under pressure to said first and second fluid operable means to charge the same with fluid under pressure and cause said first fluid operable means to said entrapped hydraulic fluid to permit movement of the pump to the said second position as actuated by the last-mentioned means to reverse the flow of fluid from the pump to the motor.

11. In combination, a hydraulic motor including reciprocable. ram means; a reversible discharge pump; means forming a hydraulic circuit between said pump and said hydraulic motor for reciprocating said ram means in both directions; and an hydraulic control means for reversing the direction of flow of fluid from said pump to said motor for reciprocating said ram; said control means including fluid operable means for actuating said pump to cause discharge therefrom in.

one direction, a second fluid operable means hydraulically connected with said first fluid operable means for governing the action thereof, means for momentarily supplying fluid under pressure to said first and second fluid operable means to charge the same with fluid under pressure and cause said flrst fluid operable means to actuate said pump to cause discharge in said one direction and cause said second fluid operable means to trap fluid in said flrst fluid operable means to retain the pump in the said position, means for continuously urging said pump to a second position to reverse the flow of fluid from the pump to the motor, and pressure means for actuating said second fluid operable means for -releasing the said entrapped hydraulic fluid to permit movement of the pump to the said second position as actuated by the last-mentioned means to reverse the flow of fluid from the pump to the motor.

12. In combination, a hydraulic motor including reciprocable ram means; a reversible dis charge pump; means forming a hydraulic circuit between said pump and said hydraulic motor for reciprocating said ram means in both directions; and an hydraulic control means for reversing the direction of flow of fluid from said pump to said motor for reciprocating said ram; said control means including fluid operable means for actuating said pump to cause discharge therefrom in one direction, a second fluid operable means hydraulically connected with said first fluid operable means for governing the action thereof, means for momentarily supplying fluid under pressure to said first and second fluid cperable means to charge the same with fluid under pressure and cause said first fluid operable means to actuate said pump to cause discharge in said one direction and cause said second fluid operable means to trap fluid in said first fluid operable means to retain the pump in the said position, means for continuously urging said pump to a secend position to reverse the flow of fluid from the pump to the motor, and means hydraulically connecting said second fluid operable means with the discharge side of said pump for actuating said second fluid operable means for releasing the said entrapped hydraulic fluid to permit movement of the pump to the said second position as actuated by the last-mentioned means to reverse the flow of fluid from the pump to the motor.

13. In combination, a hydraulic motor including reciprocable ram means; a reversible discharge pump; means forming a hydraulic circuit between said pump and said hydraulic motor for reciprocating said ram means in both directions; an hydraulic control means for reversing the direction of flow of fluid from said pump to said motor for reciprocating said ram; said control means including fluid operable means for actuating said pump to cause discharge therefrom in one direction, a second fluid operable means hydraulically connected with said first fluid oper- 29 able means for governing the action thereof, means for momentarily supplying fluid under pressure to said first and second fluid operable means to charge the same with fluid under pressure and cause said first fluid operable means to actuate said pump to cause discharge in said one direction and cause said second fluidoperable means to trap fluid in said first fluid operabl means to retain the pump in the said position, means for continuously urging said pump to a second position to reverse the flow oi fluid from the pump to the motor, pressure means for actuating said second fluid operable'means for releasing the said entrapped hydraulic fluid to permit movement of the pump to the said second position as actuated by the last-mentioned means to reverse the flow of fluid from the pump to the motor, and position-responsive means actuated as a result of a. predetermined movement of said ram and independent of pressure for releasing the said entrapped hydraulic fluid to permit movement of the pump to the said second position to reverse the flow of fluid from the pump to the motor.

14. In combination, a hydraulic motor including reciprocable ram means; a reversible discharge pump; means forming a hydraulic circuit between said pump and said hydraulic motor for reciprocating said ram means in both directions; an hydraulic control means for reversing the direction of flow of fluid from said pump to said motor for reciprocating said ram; said control means including fluid operable means for actuating said pump to cause discharge therefrom in one direction, a. second fluid operable means hydraulically connected with said first fluid operable means for governing the action thereof, means for momentarily supplying fluid under pressure to said first and second fluid operable means to charge the sam with fluid under pressure and cause said first fluid operable means to actuate said pump to cause discharge in said one direction and cause said second fluid operable means to trap fluid in said first fluid operable means to retain the pump in the said position, means for continuously urging said pump to a. second position to reverse the flow of fluid from the pump to the motor, pressure means for actuating said second fluid operable means for releasing the said entrapped hydraulic fluid to permit movement of the pump to the said second position as actuated by the last-mentioned means to reverse the flow of fluid from the pump to the motor, position-responsiv means actuated as a result of a. predetermined movement of said ram and independent of pressure for releasing the said entrapped hydraulic fluid to permit movement of the pump to the said second position to reverse the flow of fluid from the pump to the motor, and means for selectively making either of the last two mentioned means active or inactive to select between pressure reversal or position reversal of said ram.

15. In combination, a hydraulic motor including reciprocable ram means; a reversible discharge pump; means forming a hydraulic circuit between said pump and said hydraulic motor for reciprocating said ram means in both directions; an hydraulic control means for reversing the direction of flow of fluid from said pump to said motor for reciprocating said'ram; said control means including fluid operable means for actuating said pump to cause discharge therefrom in one direction, a second fluid operable means hydraulically connected with said first fluid operable means for governing the action thereof, means ior momentarily supplying fluid under pressure to said first and second fluid operable means to charge the same with fluid under pressure and causesaid first fluid operable means to actuate said pump to cause discharge in said one direction and cause said second fluid operable means to trap fluid in said first fluid operable means to retain thepump in the said position, means for continuously urging said pump to a second position to reverse the flow of fluid from the pump to the motor, pressure means for actuating said second fluid operable means for releasing the said entrapped hydraulic fluid to permit movement of the pump to the said second position as actuated by the last-mentioned means to reverse the flow oi fluid fromthe pump to the motor, and fluid operable means rendered active upon reversal of said pump and actuated by the pressure on the pressure side of the ram for bypassing the delivery from the pump and the pressure side of the ram to'the opposite side of the ram unti1 the pressure on the aforesaid pressure side of the ram has reduced to a predetermined value.

16. The combination with a reversible hydraulic motor; of means forming a hydraulic circuit with said motor for operation thereof in both directions; and control means including a flow-controlling member movable for reversibly controlling the flow of fluid to the motor, a fluid chamber having movable means therein connected to the said member, means for supp yin fluid under pressure to said chamber and for entrapping the fluid therein for positioning said member to place said motor on forward operation, fluid operable means responsive to fluid pressure to urge said member away from its last mentioned position, pressure relief means for releasing fluid from said chamber to permit the positioning of said member by said fluid operable means to place said motor on reverse operation, and means hydraulically connecting said fluid operable means with said motor to receive pressure fluid therefrom during its forward operation.

17. The combination with a hydraulic motor having reciprocable ram means; of means forming a hydraulic circuit with said ram for operating the same upon a forward stroke and a reverse stroke; and control means for controlling the direction of flow of fluid to the ram for operating the same, said control means including a'fluid flow-controlling member, means forming a fluid chamber having movable means therein operably connected to a flow-controlling member, means for supplying fluid under pressure to said chamber for operating said flow-controlling member to place said ram on a forward stroke, means for cutting ofl said supply to said chamber to trap fluid therein and retain said ram on said forward stroke, pressure actuated means for releasing fluid from said chamber for operating said flow-controlling member to place said ram on a reverse stroke, hydraulically actuated means actuated by a predetermined pressure applied upon the ram during the forward stroke thereof for hydraulically actuating said releasing means to automatihaving reciprocable ram means; or means form- 31 ing a hydraulic circuit with said ram for operating the same upon a forward stroke and a reverse stroke and control means for controlling the direction of flow of fluid to the ram for operating the same, said control means including a fluid flow-controlling member, means forming a fluid chamber having movable means therein operably connected to said flow-controlling member, means for controlling flow of fluid to and from said chamber for causing actuation of said flow-controlling member including means for supplying fluid to and entrapping said fluid in said chamber for moving the flow-controlling member in one direction and means to release said fluid from the chamber to control movement of the flow-con trolling member in the opposite direction as actuated by means continuously urging said flow controlling member against the trapped fluid, and means actuated by movement of the ram for changing the volume of said chamber and thereby proportionately shifting the flow-controlling member to reduce the volume of fluid delivered to the ram and slow down its movement.

19. The combination with a hydraulic motor having reciprocable ram means of means forming a hydraulic circuit with said ram for operating the same upon a forward stroke and a reverse stroke; and control means for controlling the direction of flow of fluid to the ram for operating the same, said control means including a fluid flow-controlling member, means forming a fluid chamber having movable means therein operably connected to said flow-controlling member, means for controlling flow of fluid to and from said chamber for causing actuation of said flow-controlling member including means for supplying fluid under pressure to said chamber and entrapping the said fluid therein for moving the flowcontrolling member in one direction and means to release the said fluid from the chamber to control movement of the flow-controlling member in the opposite direction as actuated by means continuously urging said flow controlling member against the trapped fluid, means actuatedv by movement of the ram for changing the volume of said chamber and thereby proportionately shifting the flow-controlling member to reduce the volume of fluid delivered to the ram and slow down its movement, said last mentioned means including means to again change the volume or ment thereof.

20. A control mechanism for a hydraulically interconnected pump and motor; the control mechanism including a flow-controlling member for reversing the delivery of fluid from the pump to the motor, flrst fluid operable means connected to said flow-controlling member for actuation thereof, means for temporarily delivering actuating fluid under pressure to said first fluid operable means to charge the same with fluid under pressure for moving said flow-controlling member in one direction to direct the fluid under pressure from the pump to the motor in one direction, means for continuously urging said flow-controlling member in'an opposite direction against the action of said fluid pressure to reverse the direction of flow of fluid from the pump to the motor, other fluid operable means hydraulically connected with said first fluid operable means to entrap said actuating fluid therein to prevent said urging means from moving said flow-controlling member and actuated by fluid pressure to release said entrapped fluid to permit movement of said flow-controlling member, and separate means for releasing the entrapped fluid from said first fluid operable means to permit movement of said flowcontrolling member in the said opposite direction.

HOWARD F. MACMIILIN.

REFERENCES CITED The following references are of record in the tile of this patent:

UNITED STATES PATENTS Number Name Date 1,595,755- Brooks Aug. 10, 1926 1,606,426 Justen Nov. 9, 1926 1,847,073 Ernst Mar. 1, 1932 2,163,627 Peterson June 27, 1939 2,248,076 Harrington July 8, 1941 2,274,226 Wiedmann Feb. 24, 1942 2,280,392 Herman Apr. 21, 1942 2,283,168 Ernst May 19, 1942 2,367,241 Stacy Jan. 16, 1945 

